-LRB- CNN -RRB- -- As the globe has become increasingly outfitted with wi-fi hotspots and cell phone towers , the skies have long been the last refuge from constant connectivity . That 's changing , however , as more airlines are realizing wi-fi 's earning potential .

By its own estimate , one of the fastest-growing companies in America is Gogo , which was the first to successfully hook up planes with internet . It has since installed systems on several U.S. carriers , including Delta , American and US Airways .

According to its CEO , Michael Small , Gogo 's profits grew from $ 37 million in 2009 to $ 112 million in the first six months of 2012 .

`` We 're now on over 1,600 commercial aviation jets , which is nearly half the U.S. fleet . We 've done that in four years , which is extraordinarily fast , '' says Small . `` In just a few more years , it will be done in America . ''

Watch video : In-flight wi-fi takes off

Though airlines pay to install the equipment , they also reap the rewards ; Gogo charges the customers for internet usage -- between $ 5 and $ 20 , depending on flight duration -- and shares its revenue with the carriers .

`` More travelers are aware of our service , and many of them want it , '' says Small . `` One in five say they will switch a flight to get our service . ''

The drawback with Gogo 's system is that it uses an air-to-ground network of cell phone towers it built across the United States -- each with a 250-mile radius of coverage -- meaning its wi-fi is n't available when flying over water . Internet on Gogo-outfitted planes is therefore limited to domestic flights . This is where California-based firm Row 44 swoops in .

Row 44 also installs wi-fi on airplanes , though unlike Gogo , it relies on a satellite system , meaning passengers can access internet even when flying over the ocean .

`` This is a distinct advantage , given that two-thirds of the planet is covered in water , '' notes John LaValle , Row 44 's CEO . Also , satellite systems give passengers more options , due to better bandwidth .

`` Air-to-ground has certain inherent limitations in terms of the amount of data that can be processed through the network of cell towers on the ground -- for example , live TV really is an impossibility , '' says LaValle , whose company also offers that service as part of its package . `` In a satellite environment , you 're able to get much more data through the pipe . ''

See also : Airplane phone calls to become standard ?

But the satellite system is substantially more expensive than using cell-phone towers , and has the added drawback of taking longer to install . As airlines lose money for every day a plane is out of commission , this can make the process rather costly . Some carriers , however , find it 's worth the price .

Mango Airlines and Southwest are among the airlines using Row 44 's service , with Icelandair soon to follow . What 's more , Norwegian Air Shuttle , which has also joined the fray , has just this month started offering wi-fi to passengers free-of-charge -- the first airline in Europe to do so .

`` We had a trial period where we offered it free to passengers , and we saw increases on those routes ; it went up volumes , '' notes Boris Bubresko , head of business development for Norwegian Air Shuttle . `` After that , we decided to keep it free . ''

At the moment , connectivity is a perk ; airlines that provide wi-fi or mobile services on board stand out . This will change , though , as customers increasingly start to expect the amenity , rather than merely appreciate it . LaValle feels that era has already dawned .

He says : `` I was on a plane recently that was n't wi-fi equipped , and this guy sitting across the aisle opened up his laptop and he could n't find the hotspot . He slammed it down and said , ' I ca n't believe this , I really needed to get a lot of work done on this flight ! '

`` I think we 're already at that point where everyone fully expects connectivity . ''

Is it time for all flights to offer wi-fi ? Would you pay for in-flight wi-fi , or should it be free ? Leave a comment below .

Daisy Carrington contributed to this report

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More airlines providing Wi-Fi on their flights

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Norwegian Air first airline in Europe to offer free Wi-Fi

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Gogo system installed on 1,600 U.S. jets , according to CEO

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Row 44 provides satellite-based system that can access internet even over the ocean